Technical Field
This application relates to a laser probe for use in ophthalmic procedures and more particularly to a multi-spot laser probe for use in photocoagulation therapy.
Description of Related Art
State-of-the-art laser photocoagulation therapies have been used for some time to deliver a multi-spot laser beam to retinal tissue. Multi-spot laser beams enhance the areal coverage of the therapy, increasing the speed and reducing the invasiveness of the technique. Some attempts to create a multi-spot laser probe have used a fiber bundle including a plurality of fibers. The fiber bundle is coupled to the laser source in the proximal end of the probe and delivers the laser light from multiple fibers at the distal end of the probe. One problem that arises with fiber bundle probes is that the telecentric laser beam transmitted to the tissue from the distal end of the multiple fibers should be directed into different angular directions to distribute the resulting laser beam spots on a wide area of the retina. To provide such wide area distribution, multi-spot/multi-fiber laser probes have been developed having the distal ends of the fibers bent into the desired angular directions. However, such bending is cumbersome, increases costs, and also increases the probe diameter at the distal end, which undesirably increases invasiveness.
Some attempts to cure the problem of distribution of laser spots in the retinal tissue involve the use of a GRIN lens at a distal point or end of the probe. For example, a fiber bundle may be coupled to a GRIN lens at the distal end, so that the multi-spot pattern can be projected onto the retina at the desired distance and magnification. However, this approach has various problems.
One problem is that using the GRIN lens introduces a thermal management challenge at the distal end of the probe. Indeed, even a slight coupling inefficiency between the fiber bundle and the GRIN lens generates an undesirable amount of heat trapped at the interface that is difficult to remove. The distal end of the probe typically has reduced dimensions to reduce invasiveness. Thus, heat generated at the distal end is accumulated there, since the heat conductive elements in the probe have too small dimensions to conduct all the heat away. Accordingly, the fiber-GRIN lens interface is sometimes referred to as a hotspot. As the temperature of the probe tip raises, optical elements within the tip, including the GRIN lens, may become misaligned or loosen.
Another problem is that the overheating-related malfunction takes place inside the eye, multiplying the associated risk factors. As an example, the GRIN lens and other elements may become loose, thus creating the risk of falling inside the eye, a highly undesirable outcome.
A third drawback of the existing GRIN lens designs is that the whole probe, which includes the GRIN lens, the fiber bundle, the cannula with a customized adapter, the handpiece and the fiber connectors all belong to a disposable, discarded after each procedure. Each procedure requiring new disposables raises the total cost of the procedures and thus reduces the availability of the procedure.
Accordingly, there is a need for improved multi-spot laser probes that are thermally robust and reduce the risk of damaging the tissue by heat or loose components. There is also the need for a probe composed of mostly reusable components, with only a small portion disposable.